Summary: Unlike conventional biochemical and molecular approaches, DNA microarray technology represents new era in biological science that brings along a new set of interesting paradigms. This technology can enable discovery of unknown patterns and biological processes without a piori assumptions. One can assess status of thousands of genes at once which was not possible by conventional biochemical/molecular biology means. It is believed that this technology will impact on the development of new sets of biotechnology products. After establishing a CBER/NCI Interagency Agreement (IAG), a microarray laboratory was developed. This laboratory has been renovated, equipments purchased and now operational. Research programs focus on 1) development of oligonucleotide arrays for the identification of potential presence of adventitious agents in cell substrates used to manufacture biological products e.g., vaccines, cell therapy products, gene therapy products, tissues, recombinant proteins and antibodies or presence of these agents in the products themselves 2) developent of oligonucleotide chips containing genes from human pathogens to be used for detecting pathoges in affected population. These chips will help identify specific gene expression changes in target tissues by specific pathogens for data base development and future identification of pathogens in infected population. Expression of different genes will help identify protein targets for development of therapeutic agents in countering bioterrorism 3)development of tests for identity of therapeutic tumor vaccines by expression profiling. 4) characterization of identity, differentiation state and quality of human embryonic stem cell and adult stem cell products. 5) determination of quality of cell substrates by gene expression profiling. We have recently investigated and compared gene expression profile of 293 cells (used to manufacture adeno virus vectors for gene therapy) that were grown to 90% confluence or over confluence compared to 50% confluent cells. Cells that were over confluent showed up regulation of stress related genes (e.g., P4HA1, procollagen-proline; TXNIP, thioredoxin interacting protein; ALDOA, aldolase A; ENO2, enolase 2; and LDGA, lactate dehydrogenase A). However, 90% confluent cells did not show much difference compared to 50% confluent cells. Since master cell banks are often grown in bioreactors to produce viral vectors, cell therapy products, recombinant proteins, antibodies, or vaccines. The quality of these cells cannot be viewed visually or evaluated rapidly and thus they can be inadvertently grown to overconfleunce which may results into sub optimal quality of cell substrates. Our research may provide rapid screening of these cells prior to large scale manufacture of intended product. To undertake above mentioned projects one needs access to good quality chips for hybridization. We have recently begun production of oligonucleotide chips containing more than 17,000 human genes. These chips are being tested for quality control and soon they will be ready for these exeperiments and to be distributed to any CBER, FDA or NCI scientists for use in their research.